Mountain in Thessaly (4)
I believe the answer is:
ossa
'mountain in thessaly' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ossa that I've seen before include "Hard things" , "To pile Pelion upon - is to make even greater" , "mountain in Thessaly" , "famous mount" , "So as to turn to bones" .)